As such hydraulic control devices, a device is conventionally proposed which is mounted on a vehicle including an engine and an automatic transmission, and which includes: a mechanical pump that is operated by power from an engine to generate an oil pressure; a linear solenoid valve that regulates the oil pressure from the mechanical pump to output the regulated oil pressure from an output port to an output port oil passage; an electromagnetic pump that generates an oil pressure by an electromagnetic force to output the generated oil pressure from a discharge port to a discharge port oil passage; a relay valve that has an input port (mechanical pump-side input port) connected to the output port oil passage, an output port connected to a clutch oil passage for supplying an oil pressure to a starting clutch, an input port (electromagnetic pump-side input port) connected to the discharge port oil passage, and a drain port connected to a drain oil passage, and that is operated by a signal pressure generated based on the oil pressure from the mechanical pump to allow corresponding ones of the ports to communicate with each other and shut off communication between corresponding ones of the ports; and a check valve that is attached to the drain oil passage and that is opened when an oil pressure equal to or higher than a set pressure is applied to the drain oil passage (see, e.g., Patent Document 1). When the signal pressure is equal to or higher than a predetermined pressure, the relay valve allows the mechanical pump-side input port to communicate with the output port, allows the electromagnetic pump-side input port to communicate with the drain port, and shuts off communication between the electromagnetic pump-side input port and the output port (first state). When the signal pressure is lower than the predetermined pressure, the relay valve allows the electromagnetic pump-side input port to communicate with the output port, shuts off communication between the mechanical pump-side input port and the output port, and shuts off communication between the electromagnetic pump-side input port and the drain port (second state). In the hydraulic control device configured as described above, if automatic stop conditions such as the vehicle being in a stopped state are satisfied and the engine is stopped, the mechanical pump is stopped, and the signal pressure becomes lower than the predetermined pressure, so that the relay valve switches from the first state to the second state. The engagement pressure of the starting clutch can therefore be held at a predetermined standby pressure by operating the electromagnetic pump. Accordingly, the next time the engine is started, the starting clutch can be quickly engaged, and the vehicle can be smoothly started.
[Patent Document 1] Japanese Patent Application Publication No. 2012-122560 (JP 2012-122560 A)